Pneumatic conveying apparatus for material is disclosed in German Patent Specification No. A-33 09 210.9. The discharge capacity of such pneumatic conveying apparatus can be increased by transferring material from the storage chamber to the conveyor vessel and reduced by transferring material from the conveyor vessel to the storage chamber. Such a conveying apparatus is distinguished by the fact that changes in the conveying capacity can be made very quickly and it is possible to keep the conveying capacity constant with great accuracy.
According to the German patent specification the known conveying apparatus is calibrated as follows:
With the material supply connection closed, a specific filling level first is set in the conveyor vessel and kept constant by means of the pressure in the storage chamber. The pneumatic conveying pressure thus set in the conveying vessel is measured. Then the reduction in weight of the whole system which occurs during the specific conveying interval is determined and from this the conveying capacity, i.e., the quantity of material discharged per unit of time, is calculated. In this way the first point of the desired function (conveying capacity as a function of the pneumatic conveying pressure) is obtained. Then the same process is repeated, setting another filling level in the conveyor vessel and thus another conveying capacity. By repeating this measurement a number of times any number of points of the desired calibration function can be obtained.
When using the known calibration method it is necessary to alter the conveying capacity during calibration. However, for operational reasons this is not generally desirable since such calibration frequently has to be carried out while the pneumatic conveying apparatus is running and the pneumatic conveying capacity is predetermined by the consumer. For example, it is most undesirable to have to alter the burner capacity during the calibration of a pneumatic conveying apparatus which serves to supply fuel to a burner.
A principal object of the invention is to provide a method of calibration wherein the gauging can be carried out without restricting the running of the apparatus, and in particular without its being necessary to alter the pneumatic conveying capacity. On the other hand the calibration method should be designed so that alterations in the pneumatic conveying capacity which are caused by the running of the apparatus and which may occur during the calibration do not disrupt the calibration process.